Here is another source:
"Walter Breen's Complete Encyclopedia Of U.S. And Colonial Coins" by Walter Breen and "Private Gold Coins and Patterns of the United States" by Donald H. Kagin.

There were some privately minted gold coins like this example from Kellogg & Company. That's not to say this is one of them. Would need to see the reverse. Also, is it attached to a money clip or some sort of jewelry?

Kellogg & Company issued some $20 gold coins like this that were 90% gold and 10% silver and copper. This could be worth more than a plain money clip but can't say for sure without seeing clearer photos of both sides.